U.S. Pat. No. 3,642,775 (Assigned to: Ciba Giegy Corporation) describes the preparation of compound of formula I from compound of formula II.

The compound of formula II is reacted with phosgene in toluene and subsequently with ammoniacal ethanol to yield compound of formula III. Hydrolysis of compound of formula III with dilute mineral acid gives the desired product, compound of formula I.
U.S. Pat. No. 5,808,058 (Assigned to M/s Trifarma) describes a different method for the synthesis of compound of formula I. Compound of formula II is subjected to direct carbamoylation with isocyanic acid generated in situ from cyanate and acid to generate compound of formula III which on acid hydrolysis furnishes the desired product.
Different routes for the preparation of compound of formula I are suggested in prior art starting from compound of formula II. The compound of formula II is an essential intermediate for preparing compound of formula I.
GB patent specification 943,277 describes the process for the preparation of compound of formula II, intermediate for preparing compound of formula I from compound of formula IVa.

The process exemplified in this patent discloses treating compound of formula IVa (X=CH3) with alkali metal hydroxide to yield monobromoazepine, compound of formula V after 14 hours at room temperature.

The compound of formula V is then refluxed with excess alkali metal alkanoate for 18 hours to result in compound of formula II. Also disclosed is direct conversion of compound of formula IVa to compound of formula II in about 32-40 hours. The process of the present invention uses a different starting material to prepare compound of formula II in shorter reaction times.
We have now developed a novel process for preparation of 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine-5-carboxamide, compound of formula I, in substantially pure form starting with compound of formula IVb.

The process of the present invention is advantageous as it prepares compound of formula II from compound of formula IVb in shorter reaction times. The compound of formula II is then converted to compound of formula I.